The primary objectives of this project are investigations on the damage to renal grafts inflicted by humoral antibodies. To this end, the role of humoral transplantation antibodies in hyperacute real graft rejection has been extensively studied. The putative role of transplantation antibodies in forming immune complexes responsible for the late rejection of renal graft will be explored. In vitro reactions of transplantation antigens and antibodies will be further investigated using primarily the procedures developed in this laboratory: mixed agglutination with cell cultures, mixed agglutination with artificial cell monolayers, cytolysis in agar gel, and double diffusion in gel. The latter procedure, established just very recently, offers many new possibilities for analysis of transplantation antigens and antibodies. Identification of immune complexes composed of transplantation antigens and antibodies present in the circulation and deposited in the renal graft will be explored in depth. Further studies on xenograft rejection will be conducted utilizing the perfusion model of guinea pig heart by foreign species sera. Neutralization of foreign sera with solubilized antigens will be attempted with the aim of developing a procedure which will permit prolongation of the survival time of xenografts.